1. A class of virtual reality experiments
accessible via the Internet. These are real-time chat forums with
structure; they have multiple ‘locations’ like an adventure
game, and may include combat, traps, puzzles, magic, a simple economic
system, and the capability for characters to build more structure onto the
database that represents the existing world.

2. vi. To play a MUD. The
acronym MUD is often lowercased and/or verbed; thus, one may speak of
going mudding, etc.

Historically, MUDs (and their more recent progeny with names of MU-
form) derive from a hack by Richard Bartle and Roy Trubshaw on the
University of Essex's DEC-10 in the early 1980s; descendants of that game
still exist today and are sometimes generically called
BartleMUDs. There is a widespread myth (repeated,
unfortunately, by earlier versions of this lexicon) that the name MUD was
trademarked to the commercial MUD run by Bartle on British Telecom (the
motto: “You haven't lived 'til you've
died on MUD!”); however, this is false —
Richard Bartle explicitly placed ‘MUD’ in the public domain in
1985. BT was upset at this, as they had already printed trademark claims
on some maps and posters, which were released and created the myth.

Students on the European academic networks quickly improved on the
MUD concept, spawning several new MUDs (VAXMUD, AberMUD, LPMUD). Many of
these had associated bulletin-board systems for social interaction.
Because these had an image as ‘research’ they often survived
administrative hostility to BBSs in general. This, together with the fact
that Usenet feeds were often spotty and difficult to get in the U.K., made
the MUDs major foci of hackish social interaction there.

AberMUD and other variants crossed the Atlantic around 1988 and
quickly gained popularity in the U.S.; they became nuclei for large hacker
communities with only loose ties to traditional hackerdom (some observers
see parallels with the growth of Usenet in the early 1980s). The second
wave of MUDs (TinyMUD and variants) tended to emphasize social interaction,
puzzles, and cooperative world-building as opposed to combat and
competition (in writing, these social MUDs are sometimes referred to as
‘MU*’, with ‘MUD’ implicitly reserved for the more
game-oriented ones). By 1991, over 50% of MUD sites were of a third major
variety, LPMUD, which synthesizes the combat/puzzle aspects of AberMUD and
older systems with the extensibility of TinyMud. In 1996 the cutting edge
of the technology is Pavel Curtis's MOO, even more extensible using a
built-in object-oriented language. The trend toward greater
programmability and flexibility will doubtless continue.

The state of the art in MUD design is still moving very rapidly, with
new simulation designs appearing (seemingly) every month. Around 1991
there was an unsuccessful movement to deprecate the term
MUD itself, as newer designs exhibit an exploding
variety of names corresponding to the different simulation styles being
explored. It survived. See also bonk/oif,
FOD, link-dead,
mudhead, talk mode.